This invention relates to an antenna for use in a miniature radio receiver which may be, for example, a portable radio receiver, such as a pager receiver.
Recent requirements are such that an antenna of the type described is for use in a high frequency range, such as a frequency range between 440 and 460 megahertz, with a high antenna gain. Inasmuch as the antenna gain increases with an aperture area, as called in the art, the apreture area should be wide in order to increase the antenna gain.
A conventional antenna is usually housed in a hollow space enveloped by a housing or casing of a miniature radio receiver and is coupled to a reactance circuit to be put into operation as a loop antenna. The antenna should be reduced in size because the antenna must have a low reactance so as to be used in the above-exemplified high frequency range. Such a reduction of the antenna size inevitably results in a reduction of the aperture area and, therefore, lowers the antenna gain. The reduced antenna leaves a superfluous space in the hollow space when the housing is not changed in size. Thus, the hollow space is not effectively utilized in the receiver in which the reduced antenna is accommodated in the hollow space.
In. U.S. Pat. No. 3,736,591, issued to L. W. Rennels et al on May 29, 1973, and assigned to Motorola, Inc., an antenna is disclosed which has a U-shaped configuration and serves as a part of a housing a miniature radio receiver. The proposed antenna is effectively used in a low frequency range between 148 and 174 megahertz in cooperation with a reactance circuit connected thereto. A comparatively high antenna gain may be attained in the low frequency range in comparison with the above-mentioned antenna housed in the housing. In order to be used in the high frequency region as mentioned above, the proposed antenna should be reduced in size like in the abovementioned antenna. In addition, the housing should also be reduced in size because the antenna serves as the part of the housing. As a result, the antenna gain is inevitably lowered when used in the high frequency range.